2016 Reaxys PhD prize Symposium, Novotel London Excel, London, UK, September 22-23. Abstract. Silicon has the potential to revolutionize the energy ...
In situ Chemical Chelation and Polymer Cyclization Boosting the Stability of Lithium-ion Batteries Fathy M Hassana,b, Xingcheng Xiaob, Zhongwei Chena aDepartment of Chemical Engineering, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada. bChemical and Materials Systems, General Motors Global Research and Development 30500 Mound Road, Warren, MI 48090, USA
Abstract Silicon has the potential to revolutionize the energy storage capacities of lithium ion batteries to meet the ever increasing power demands of next generation technologies. To avoid the operational stability problems of silicon-based anodes, we propos physico-chemical alteration in micro-reactor into the electrode. This capitalizes on covalent bonding of Si nanoparticles (SiNP) with sulfur-doped graphene (SG) and cyclized polyacrylonitrile to provide a robust nano-architecture. This occurs during in situ chemical reaction in a microscale inside the electrode material. The hierarchical structure stabilized the solid electrolyte interphase leading to superior reversible capacity of over 1000 mAh g-1 for 2275 cycles. Furthermore, the structure synergy leads to facilitated lithium diffusion, which strongly supports our results.
Introduction The success of portable electronics and electric vehicles strongly depends on further technological progress of rechargeable batteries. Lithium-ion batteries (LIBs) are considered the most likely energy storage configuration to satisfy these demands, however this requires significant advances in terms of power density, energy density, cycle life, and safety, as well as lower production costs.
Li + 6 C (graphite) = LiC6 4.4 Li + Si = Li4.4Si
Capacity = 372 mAh/g , reaction type = Intercalation Capacity = 4200 mAh/g , reaction type = Alloying
Current technology prospective technology
volume increase to 400%, lead to degradation of the electrode structure and capacity loss
Methods & Materials Firstly, mix Silicon nanoparticles (SiNP) (~60%), Sulfur doped graphene (SG), graphitic oxide (GO) and Poly acrylonitrile (PAN) in dimethylformamide (DMF) to form homogenous mixture under ultrasonic radiation. Then, we cast the slurry on Cu current collector followed by drying in convection oven. Finally, the electrodes were cut and pressed, then subjected to a sluggish heat treatment (SHT) by slowly heating in inert gas to 450oC, then hold for 10 minutes, followed by furnace cooling.
The micro reactor
Mixing
Li
Li Si Si Si Si Si Si
Herein we introduce a new electrode design concept that capitalizes on the strong covalent interactions occurring between Si, sulfur, defects, and nitrogen. This involves wrapping SiNP with SG, and then shielding this composite arrangement with cyclized PAN.
5.5
2.5
1.75
0.25
O
+
+
S S
S S
S S
+
O S
HO O O O HO O OH O O O O O OH HO HO O O O HO HO O O HO O HO O HO O OH HO
S
O
Si
Results In the micro reactor within the electrode; 1- PAN cyclize π-conjugate.
2- Silicon Chelate to sulfur in SG and capped with c-PAN
Si
20
DTA: Exothermic Peak
Heat Flow (mW)
15
S-G-Si(B)
1.44 34
10
2
1
2.30 5
BE=-3.70eV 0
100
150
200
250
300
350
Raman: well defined D and G band
Temperature (°C)
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4000
4.0
1.8
0.8 0.6 0.4 0.2 0.0 0
500
1000
1500
2000
2500
Specific Capacity, mAh g
-1
Voltage profile
-2
2500 2000 1500 1000 500
0.1 A g
80
-1
60
3
Chg DChg
2
40
20
1
3000
0
0 0
20
40
60
80
Specific Capacity, mAh g-1
1.0
4
Efficiency, %
1.2
3000
Aerial capcity, mAh cm
-1
Specific capacity, mAh g
+
1.4
3500
Cycle stability at low rate
SG
80 2500
The treated electrode stabilizes for over 2000 cycles at high rate
2000
2Ag
60
-1
1500 40 1000 20
Traditionally designed electrode degrades rapidly
500
0 100
Cycle No.
c-PAN
Charge Discharge
3000 Cycle 1 Cycle 2 Cycle 3
1.6
Voltage, V vs Li/Li
100
100
5
BE=-0.45eV
Si
3500
-2
G-Si
4- after cycling, no Si agglomeration.
Cycle stability at high rate
3- Excellent electrochemical performance. Capacity, mAh cm
HAADF and HRTEM; SiNP/c-PAN/SG
DFT Calculation: Si strongly bind to SG more than G
Efficiency, %
-5 50
0
0 0
250
500
750
1000
1250
1500
1750
2000
2250
Cycle No.
SG_Si nanohybrid can provide a stable reversible capacity of 1033 mAh/g for more than 2000 cycles at 2A/g and with cut-off voltage 1.5 – 0.05 V. Traditionally designed electrode cannot provide a stable reversible capacity rather it decays by cycling at 2A/g
Before battery cycling SiNP are dispersed, and bond with S on surface of SG with c-PAN further connect the SiNP with SG. After battery cycling, the SiNP change to amorphous structure and spread and confine in the crinkles of SG.
Conclusion
Acknowledgements
Covalent binding of SiNP and SG along with cyclized PAN offers exceptional potential in the practical utilization of Si anodes for Li-ion battery. The synergistic effect of the covalent bonds between Si-S, the facilitated charge transfer by 3D graphene network and cyclized PAN, and the improved electrode integrity all attributed to the superior cycle performance with a high areal capacity . A rational design and scalable fabrication paves the way for the real application of Si anodes in high-performance lithium-ion batteries.
The authors would like to acknowledge financial support from General Motors, the Natural Sciences and Engineering Research Council of Canada (NSERC), the University of Waterloo and the Waterloo Institute for Nanotechnology. TEM imaging was carried out by Dr Carmen Andrei at the Canadian Center for Electron Microscopy (CCEM) located at McMaster University
References F. M. Hassan , R. Batmaz, J. Li, X. Wang, X. Xiao, A. Yu, Z. Chen, Nature Communications, 6, (2015) 8597. F. M. Hassan; A. Yu, Z. Chen, US provisional patent, filed on February 6, 2015, serial # 62/176,004 by USPTO.
2016 Reaxys PhD prize Symposium, Novotel London Excel, London, UK, September 22-23
In Situ Chemical Chelation And Polymer Cyclization Leading To Extremely Stable Lithium-Ion Batteries Fathy M Hassana,b, Xingcheng Xiaob, Zhongwei Chena aDepartment
of Chemical Engineering, University of Waterloo, Waterloo, Canada and Materials Systems, General Motors Global Research and Development, Warren, United States bChemical
Fathy M. Hassan Silicon has the potential to revolutionize the energy storage capacities of lithium ion batteries to meet the ever increasing power demands of next generation technologies. To avoid the operational stability problems of silicon-based anodes, we propose synergistic physico-chemical alteration of electrode structure during its design. This capitalizes on covalent bonding of Si nanoparticles (SiNP) with sulfurdoped graphene (SG) and with cyclized polyacrylonitrile to provide a robust nano-architecture. This occurs during in situ chemical reaction in a microscale inside the electrode material. The hierarchical structure stabilized the solid electrolyte interphase leading to superior reversible capacity of over 1000 mAh g-1 for 2275 cycles. Furthermore, the nano-architectured design lowered the contact of the electrolyte to the electrode leading to not only high coulombic efficiency of 99.9% but also maintaining high stability even with high electrode loading associated with 3.4 mAh cm-2 of areal capacity. Furthermore, the structure synergy leads to facilitated lithium diffusion, which strongly supports our results. This simple, low cost, feasible, and safe approach provide new avenues for engineering electrode structure for enhanced performance.
2.5
1.75
0.25 HO O O O HO
O
+
+
S S
S S
S S O
+
HO HO
O
HO
O O
HO O
HO
S
O
O OH
O HO
100 4000
O OH
O O
O
(b)
O HO
HO O O OH
O
(c)
5
99
3500 3000
98
2500 2000 1500 1000 500 0
4
0.1 A g
-1
97 96
3 95
Chg DChg
2
94 93
Efficiency, %
GO
-2
SG
Areal capcity, mAh cm
Si Si Si Si Si Si
5.5
PAN
-1
SiNP
Specific capacity, mAh g
(a)
92
1
91 0 0
20
40
60
90 100
80
Cycle No. 100 99
3000
5
10
15
2Ag
-1 20
25
96 95 94
30
1000
93
Efficiency, %)
0
-1
-1
-1
-1
1500
0
98 97
4Ag
1000
2Ag
2000
Charge Discharge
1Ag
2000
0.5 A g
-1
2500
0.1 A g
Specific Capacity, mAh g-1
3000
92
500
-1
1470 mAh g
2Ag
-1
-1
1033 mAh g remain 70%
91
0
90 0
250
500
750
1000
1250
1500
1750
2000
2250
Cycle No.
Figure 1. (a) Electrode composition and in-situ chemical chelation and polymer cyclization, (b and c) Lithium-ion battery cycle stability at 0.1A/g and 2 A/g, respectively. 1. F. M. Hassan , R. Batmaz, J. Li, X. Wang, X. Xiao, A. Yu, Z. Chen, Evidence of covalent synergy in siliconsulfur-graphene yielding highly efficient and long-life lithium-ion batteries" Nature Communications, 6, (2015) 8597. 2. F. M. Hassan; A. Yu, Z. Chen, US provisional patent “A preparation method of negative electrodes for lithium ion batteries”, filed on February 6, 2015, serial # 62/176,004 by USPTO
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